Although intraluminal manometry and cineroentgenography have provided much information about esophageal motor function, these examinations do not adequately record esophageal motion, particularly motion of the esophagus along its longitudinal axis. Labelling the esophageal wall, esophagogastric junction and diaphragmatic hiatus with implanted metal markers, however, permits direct observation and recording of esophageal movement. The proposed study describes a plan of evaluating, in humans and in animals, esophageal motion associated with peristalsis, respiration and other physiologic events. Esophageal dynamics will be studied in individuals and animals with normal esophageal function and in others with altered esophageal motor function caused by esophagitis, hiatal hernia, drugs, vagotomy and other conditions. In consenting human adults, the esophagus and diaphragmatic hiatus will be labelled with small metal markers at time of elective thoracic or abdominal surgery performed for other reasons. Esophagi of cats, opossums and monkeys will be labelled by a technique shown not to cause important changes in esophageal motility or histology. A major aim of the study is to characterize the mechanisms associated with lower esophageal sphincter (LES) opening and the LES antireflux mechanism. Such information will permit better design of surgical hiatal hernia repair or valve producing procedures to prevent gastroesophageal reflux. Additional goals include evaluation and improvement of the systems used for measuring esophageal pressure, improvement and comparison of the x-ray and manometric exams of esophageal motor function.